Whitney Houston had "a moderate level" of cocaine in her system when she was found underwater and unresponsive in a hotel room bathtub last month, while the official cause of her death was accidental drowning, Los Angeles County Chief Coroner Investigator Craig Harvey said on Thursday, March 22.

His office released the toxicology results reached following an autopsy and investigation. Cocaine and a pre-existing condition of atherosclerotic heart disease were determined to be contributing factors to the death of the 48-year-old pop star, who had battled substance abuse for years and underwent several rehab stints.

"We believe that something happened that caused her to go down and we know that when she slipped under the water, she was still alive," he said. "We have evidence of drowning. There was water in the lungs. Chances are, had she not had the pree-xisting heart disease and cocaine use, she may not have drowned."

He said investigators were not able to determine for sure if Houston had a heart attack.

The autopsy results indicted approximetely 60 percent narrowing of the artery," he said. "So the finding of atherosclerotic heart disease suggest a cardiac event, complicated by the cocaine use."

When asked how much cocaine was found in her system, Harvey said: "A moderate level. The level indicates an acute dose, not probably too much before she collapsed in the shower area. The toxicology finding suggest chronic usage [of cocaine]. The cocaine causes the heart to beat faster, the arteries to constrict, which can create a problem and set you up for a cardiac event."

Traces of marijuana, the anti-anxiety medication Xanax, the muscle relaxant Flexeril and the allergy drug Benadryl were also found in her system but the traces were too low and were not listed as contributing factors in her death, Harvey said, adding that no trauma or foul play is suspected. He said the singer was otherwise healthy at the time of her death.

Houston's family was notified about the toxicology results before they were released to the press, Harvey said, adding that a full autopsy report is expected to be published within two weeks. The singer is survived by daughter Bobbi Kristina, 19, and ex-husband, singer Bobby Brown.

Houston underwent treatment for drug and alcohol abuse in 2003 and 2004 and relapsed in May 2011.

In what has become an infamous 2002 interview with ABC News' Diane Sawyer, Houston said she consumed alcohol, cocaine, marijuana and prescription drugs at different points during her career but denied using crack cocaine, saying: "Crack is cheap. I make too much for me to ever smoke crack. Let's get that straight, Okay? I don't do crack. I don't do that. Crack is whack."

"I partied a lot," she added. "Trust me, I partied my tail off. You get to a point where you know the party's over."